The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Controlling the amount of fuel and air to be delivered per cylinder for a four stroke internal combustion engine is important to achieve optimum performance. Proper timing of intake and exhaust valves also provide for better performance. Conventional engines include camshafts that regulate the timing of the valves. The rotation of the camshaft can be controlled to ensure proper timing of each valve. In addition cam phasers may be included to alter the position of the camshafts relative to the crankshaft which provides for further opportunities to properly adjust the timing of each valve.
The placement of fuel injectors within the engine and the control of fuel injection timing also impacts engine performance. Port fuel injection engines locate one fuel injector per cylinder, mounted in the intake manifold near the cylinder head. Each injector may be controlled either individually or by groups to inject fuel near the intake valve. Spark-ignited direct injected (SIDI) engines locate one fuel injector per cylinder, mounted directly over the cylinder head. Each injector is controlled individually to inject fuel directly into the cylinder.
Conventional methods of controlling fuel during idle conditions, whether in a port fuel injected engine or a SIDI engine, intentionally retard spark timing in order to provide a reserve torque. Spark timing is then advanced when a request for torque is initiated. This allows the engine to respond to load demands (i.e. power steering “cramp” input) during idle operation. Retarding spark at idle provides for sub-optimal efficiency.